Orientation of amorphous poly(ethylene terephthalate) by tensile drawing, roll‐drawing, and die‐drawing

Abstract

Orientation of initially amorphous poly(ethy1ene terephthalate) fllms and sheets was carried out by means of tensile drawing in a tensile tester, roll-drawing using a series of four rolling stations, and by die-drawing. The drawing temperature was 80 and 90°C and drawing rate ranged from 2 to 20 cm/min in the different processes. Crystallinity was observed to increase with draw ratio for all these processes. The onset of crystallinity development depends on the drawing rate. The glass transition temperature was essentially constant and crystallization temperature decreased with increasing draw ratio. The trans conformel-s content was observed to increase with draw ratio at the expense of the gauche conformers for the three processes. The orientation of the trans conformers increases readily from the beginning of draw and saturates rapidly. The orientation of the gauche conformers was negligible. Some differences are observed for the behavior of the 1020 and 730 cm-' benzene ring bands, which may be due to differences in the benzene ring configuration at the surface as a result of different deformation mechanisms for the die and roll-drawing. However, further investigations to elucidate this hypothesis are needed. The mechanical properties obtained in the longitudinal direction increased for all the processes. In the transverse direction, the roll arid die-drawing processes induced a decrease in modulus and strength with increasing draw ratio, similar to that observed for uniaxial orientation. This indicates that these processes are mainly uniaxial, despite the plane strain nature of the deformation.

Roll-drawing and die-drawing of toughened poly(ethylene terephthalate). Part 1. Structure and mechanical characterization

“…The drawn sheet leaving the second set of rolls is subsequently cooled by the successive rolls. The traction force exerted by the traction rolls produces pronounced anisotropy in the roll direction and little change in the transverse properties from those of the isotropic material [35,36]. When no traction pull is exerted on the material, the process resembles the conventional rolling process that produces biaxial orientation in the sheet [37,38].…”

Molecular orientation of extruded PET/LCP blend films. Part I: Polarized infrared spectroscopy

“…The angle a is 228 for the 1474-cm À1 band, 35,36 348 for the 974-cm À1 band, 27,37 and 218 for the 1340-cm À1 band. 27,29,31,38,39 The value of a is unknown for the 1630, 1601, 1453, and 1370-cm À1 bands. To overcome variations in the overall intensity of the spectra, arising from effects like surface quality and thickness variation of the samples, all spectra were normalized by examining the 794 and 1410-cm À1 bands, which are insensitive to orientation as well as crystallinity.…”

Structural development of poly(ethylene terephthalate) during uniaxial stretching above the glass‐transition temperature: Study of the statistical influence of the stretching variables

“…The phases were defined by Ajji and coworkers, 17,18 using Fourier transform infrared spectroscopy, as (1) an amorphous phase, composed solely of gauche conformers; (1) a mesophase, consisting of gauche and highly oriented trans conformers; and (3) a crystalline phase, consisting only of trans conformers. The mesophase has been the focus of many studies.…”

“…Many studies have been conducted to characterize this material under different stretching conditions and to relate those to its structural development. [2][3][4][5][6][7] Different techniques were used, from postmortem techniques based on densiometric measurements, [8][9][10] fluorescence spectroscopy, [10][11][12][13][14] Raman spectroscopy, 15,16 IR spectroscopy, 11,[17][18][19][20][21][22] Xray diffraction, [3][4][5][6]8,11,17,18,[22][23][24][25][26][27][28][29][30] optical birefringence (BIR), 3,6,10,16,17,[30][31][32][33]…”